Smoking and Prognostic Factors in an Observational Setting in Patients with Advanced Non-Small Cell Lung Carcinoma

Background: This prospective observational study estimated the effect of prognostic factors, particularly continued smoking during therapy, on survival in advanced non-small cell lung cancer (NSCLC) patients receiving gemcitabine-platinum. Further, prognostic factors were used to build a survival model to improve prognosis prediction in naturalistic clinical settings. Methods: Eligibility criteria included: Stage IIIB/IV NSCLC, no prior chemotherapy, and Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1. A Cox regression model was constructed and validated by randomizing patients into two datasets (Construction [C]: Validation [V]; 3: 1 ratio). Country, disease stage, hypercalcemia, "N" factor, weight reduction, performance status, and superior vena cava obstruction were pre-defined variables forced into the model. Continued smoking was tested with adjustment for these variables. Results: One thousand two hundred and fourteen patients (C=891 and V=323) were enrolled. The final predictive model, established in the Construction dataset, identified four significant (p <= 0.05) and independent predictors of survival, which were disease stage, performance status, gemcitabine-platinum regimen, and T-stage. Smoking during therapy was not significantly associated with survival (Hazard Ratio [95% CI]: 0.955 [0.572, 1.596], p=0.8618; versus never smokers). Conclusions: Although continued smoking during therapy was not significantly associated with shorter survival, the model developed in this study forms an evidence-based approach to assessing prognosis in advanced stage NSCLC.